don't take the rejections personally. you're coming in at a time when every site is becoming more picky due to stiffer competition. try to vary your subjects and then see what they take. like you said, the ones they took is no better than the ones they rejected. so try to go one step further and make the next submitted batch a little better and different. good luck.

Did you submit one type of images? If so, try varying subjects .

BigStock has a reviewer who enjoys rejecting newbies with "this is a snapshot" rejections. It's someone close to the description of FlemishDreams "Atilla", that you probably know from those with this forum for the past years.
 
Since your rejection reason is similar to that of DT, either you had the arseluck of getting the same sadistic reviewer moonlighting for both sites , or you need to rethink what to submit.

Based on what has been happening here with others before you getting the same "have enough..." rejections from DT,  I would say submit something different.

Chins up, keep going ... and accept this as a reality.  Go outside and kick a tin can; go to the boxing gym and hit the punching bag, then come back in and  submit some more